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 Post subject: 1920s Brandes speaker pot-metal issues
PostPosted: Sep Thu 16, 2021 6:17 pm 
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Joined: Aug Mon 31, 2020 9:21 pm
Posts: 205
Location: 3717 NW 66th pl gainesville FL 32653
i got a couple of old 1920s brandes speakers that unfortunately have pot-metal frames that are disintegrating. one has completely broken, the other has chipping on the support. i am wondering if I can brush some kind of epoxy in the metal to keep it from breaking apart further, any ideas?
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 Post subject: Re: 1920s Brandes speaker pot-metal issues
PostPosted: Sep Thu 16, 2021 10:41 pm 
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Joined: Jan Mon 16, 2012 4:15 pm
Posts: 8110
Location: Near Brandon, Iowa
I don't think that a "brush on" approach would work well...the "rot" absolutely permeates the material, so replacing a part of it with epoxy just means that the overall piece will fail elsewhere; maybe even just a few millimeters from the bond point.

I'd suggest either allowing the unit to continue to decompose in peace, or make a mold master out of wood and cast a new frame out of metal-bearing epoxy. This would be a lot of work to salvage a tinny-sounding early loudspeaker, but you might be able to sell additional frame castings to other owners. The prospect for any financial returns seems low, however.


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 Post subject: Re: 1920s Brandes speaker pot-metal issues
PostPosted: Sep Thu 16, 2021 11:30 pm 
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Joined: Aug Mon 31, 2020 9:21 pm
Posts: 205
Location: 3717 NW 66th pl gainesville FL 32653
well since I guess i don't have much to lose I will still try epoxy on one and retrofit the other with a newer speaker. (a modern speaker with an output transformer)


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 Post subject: Re: 1920s Brandes speaker pot-metal issues
PostPosted: Sep Fri 17, 2021 2:01 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 6886
Location: Bossier City, Louisiana
Thin super glue holds VERY well! Plus it seeps into the cacks!

Use the "thin" glue and the accellerator. I have had great success!

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Dave

http://pages.suddenlink.net/davesradios/


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 Post subject: Re: 1920s Brandes speaker pot-metal issues
PostPosted: Sep Fri 17, 2021 3:41 am 
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Joined: Sep Fri 18, 2020 12:31 am
Posts: 70
Location: Dayton, WA 99328
I have two of these as well but they are different. One has pot metal, the other does not. Not sure when they made the switch but the one without pot metal works beautifully, the other does not.


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 Post subject: Re: 1920s Brandes speaker pot-metal issues
PostPosted: Sep Fri 17, 2021 3:56 am 
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Joined: Jul Mon 01, 2019 4:42 pm
Posts: 989
Location: St. Louis, MO
Seeing as you have one that's nearly complete, how hard would it be for you to take it to a local casting company and have them make you brand new frames? Making a mold is nondestructive.


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 Post subject: Re: 1920s Brandes speaker pot-metal issues
PostPosted: Sep Fri 17, 2021 3:59 pm 
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Joined: Sep Fri 18, 2020 12:31 am
Posts: 70
Location: Dayton, WA 99328
I've been dabbling in green sand casting and was thinking about trying to make an aluminum piece. To be honest, I've been afraid to take it apart, cracks around all the screws etc. It's no good like it is so let me see what I can do.


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 Post subject: Re: 1920s Brandes speaker pot-metal issues
PostPosted: Sep Fri 17, 2021 4:23 pm 
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Joined: Jul Mon 01, 2019 4:42 pm
Posts: 989
Location: St. Louis, MO
Like I said. Take it to a local casting shop. They might have a 3D scanner so you wouldn't even need to take it apart. They can scan the whole thing, then delete the speaker bits from the scan in the computer.


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 Post subject: Re: 1920s Brandes speaker pot-metal issues
PostPosted: Sep Fri 17, 2021 4:43 pm 
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Joined: Feb Sun 01, 2009 2:56 pm
Posts: 12504
Location: Victoria, Australia
ZombieElvis wrote:
Like I said. Take it to a local casting shop. They might have a 3D scanner so you wouldn't even need to take it apart. They can scan the whole thing, then delete the speaker bits from the scan in the computer.


On the right track: Even if they have not got a scanner that is not a particularly difficult thing to draw up. It is possibly printable to make it, or a casting mould, but it may be better to cut it out with a CNC.

I have used epoxy resin on some pot metal, but long term it will blow itself apart, or brittle fracture. In the case of Inertia wheels, I find its less messing about to get some Aluminium & turn another one, on the Lathe

Marc


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 Post subject: Re: 1920s Brandes speaker pot-metal issues
PostPosted: Oct Thu 14, 2021 9:30 pm 
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Joined: Aug Mon 31, 2020 9:21 pm
Posts: 205
Location: 3717 NW 66th pl gainesville FL 32653
taking it to a casting place would be way outside of my price range. I ended up scrapping one and retrofitting it and the other I saved. if I needed to make a new frame I modeled it in a cad program for 3d printing. and the original one is pretty weak like other people have been saying, but if I turn my AK 33 all the way up it is not too bad. thanks for the input.


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 Post subject: Re: 1920s Brandes speaker pot-metal issues
PostPosted: Oct Thu 14, 2021 11:52 pm 
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Joined: Feb Sun 01, 2009 2:56 pm
Posts: 12504
Location: Victoria, Australia
This is a post where a casting has been done recently viewtopic.php?f=6&t=401089.

Worth a look if you are considering making it look somewhat original?

Marcc


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